WASHINGTON – Supporters and opponents of the long-delayed Keystone XL oil pipeline from Canada jockeyed for position ahead of an expected U.S. Senate vote on legislation authorizing immediate construction of the project.

An oil industry group that supports the pipeline launched a five-state ad campaign aimed at undecided senators, while an environmental group mobilized activists to urge lawmakers to vote against any attempt to force President Barack Obama to decide the pipeline’s fate. Canada’s leaders have pushed for the project’s approval.

The lobbying came as Democrats and Republicans argued over whether to allow a vote on a bipartisan bill to end years of delay and build the proposed pipeline from Canada’s oil sands through the central United States.

The proposed pipeline would carry oil from western Canada to Nebraska, where it eventually would reach Gulf Coast refineries. Supporters say it would create thousands of jobs and help the U.S. move closer to a goal of energy independence. Opponents say the project would create few permanent jobs and reinforce the nation’s use of an energy source that worsens global warming.

Senate Majority Leader Harry Reid has said he is open to a stand-alone vote on a pipeline bill, although some Republicans said the vote should occur as an amendment to energy efficiency legislation that could reach the Senate floor as soon as Tuesday.

Republican senators have prepared amendments to the efficiency bill, including one that would block the Environmental Protection Agency from imposing rules limiting greenhouse gas emissions from coal-fired power plants.

Lawmakers from both parties also support a measure to speed approval of terminals to export liquefied natural gas, another complication as Reid and other Democratic leaders consider when and how to allow a vote on the energy efficiency bill.

Senate Minority Leader Mitch McConnell, a Republican, said it was important to include Keystone and other issues in the bipartisan energy efficiency bill.

“We should be having a debate about how to develop policies that can actually lead to lower utility bills for squeezed families, put people back to work America’s coal country … and lead to a more effective use of North American energy supplies,” McConnell said on the Senate floor, noting that the Senate has not approved a comprehensive energy bill since 2007.

Meanwhile, the American Petroleum Institute, the oil industry’s top lobbying group, announced it has begun TV, radio and online ads promoting the pipeline in five states: Colorado, Delaware, Minnesota, New Mexico and South Dakota. The ads urge senators in those states— including at least three Democrats who are publicly undecided — to approve the Keystone XL pipeline.

An environmental group was organizing a blitz of Democratic senators by email, telephone and in-person protests.

Pipeline supporters “are advertising on TV, while we are out on the streets,” said Jason Kowalski, policy director for 350.org. an environmental group that opposes the pipeline.